Question

Stars twinkle due to :

• A. atmospheric refraction
• B. atmospheric reflection
• C. scattering of light
• D. dispersion of light

Hint:

Imagine looking at something through the wavy hot air above a fire – it shimmers. Stars twinkle for a similar reason: starlight passes through Earth's unsteady atmosphere, causing it to bend randomly. This changing path makes the star's brightness and position seem to flicker.

Answer 1

The Correct Option is A

Concept: The twinkling of stars is an optical effect caused by starlight passing through Earth's atmosphere. Step 1: Understanding Starlight and Earth's Atmosphere Stars are very far away, so they appear as point sources of light. Earth's atmosphere is made of layers of air with varying temperatures and densities. This means the optical density (and thus refractive index) of air changes from point to point and fluctuates over time due to air currents. Step 2: The Phenomenon of Atmospheric Refraction Refraction is the bending of light as it passes from one medium to another of different optical density. As starlight enters Earth's atmosphere and travels through these fluctuating layers:
The light path continuously bends by small amounts.
This random bending causes the apparent position of the star to seem to shift slightly.
The amount of starlight reaching our eye also varies. Sometimes more light reaches us (star appears brighter), and sometimes less (star appears dimmer). This rapid variation in brightness and apparent position is what we perceive as twinkling. Step 3: Why other options are not the primary cause
Atmospheric reflection: While some reflection occurs, the dominant effect causing twinkling is the bending of light (refraction) through atmospheric layers.
Scattering of light: This causes the blue color of the sky but isn't the main reason for twinkling.
Dispersion of light: This is the splitting of light into colors (like a rainbow) and is not the primary cause of the twinkling effect. Therefore, atmospheric refraction is the cause of stars twinkling. Planets, being closer and appearing as extended sources, do not twinkle as much because the variations from different points on the planet average out.